The present invention relates in general to the production of extruded weather strips. More specifically, the invention concerns a weather strip intended particularly for fitting to the edge of an aperture or closure element of the body of a motor vehicle, of the type comprising a U-sectioned anchoring profile of elastomeric material provided with internal longitudinal ribs for retaining the weather strip on the edge, and a tubular sealing profile also of elastomeric material and co-extruded with the retaining profile, and in which the tubular profile and/or the anchoring profile have variable characteristics.
These variable characteristics may consist, for example, of a differentiated section of the wall of the tubular profile, a variable configuration of the anchoring profile, or even of variations in the shape or relative positioning thereof.
In the production of such weather strips, there is the problem of cutting the continuously extruded element to size in order to obtain pieces of a length which is predetermined in dependence on the fitting requirements. The cutting zones are normally coordinated with the variations in the characteristics of the extrusion. The cutting must be effected automatically, in synchronisation with the advance of the weather strip output by the extrusion head and with maximum precision, that is, exactly in correspondence with the predetermined zones. However, since the speed of advance of the extrusion may be subject to variations during extrusion, control of the cutting action cannot be directly related to this advance. It is therefore necessary to provide references on the extruded weather strip for detection by suitable sensors for controlling the cutting.
According to current techniques used by the Applicant, such references are constituted by additional parts in the form of appendages or projections formed on the weather strip directly during extrusion, in correspondence with the predetermined cutting zones, and cooperating, for example, with mechanical detectors operatively associated with the cutting unit.
This solution involves considerable complications in the weather strip extrusion process, as well as additional costs due to the need to use auxiliary equipment for obtaining the reference projection and for compensating for pressure differences which are generated according to whether the additional part is present or not in a section of the extrusion. Moreover, this projection remains on the finished weather strip and is then visible from outside, with obvious aesthetic disadvantages when the weather strip is in the mounted condition. To avoid the latter problem, it is necessary to remove the reference projection after the weather strip has been cut, which involves further production tasks.